The concept of installing a concrete wall without prior excavation is not new to this invention. Foundations for large office buildings have been installed using a method whereby an auger manipulated by a large crane, drills down into the ground to a desired depth, e.g., 20 feet to create a hole of loosened soil. The auger has a hollow shaft and a cement based grout is pumped through the shaft to the auger head. As the auger is withdrawn, the auger blades mix the grout and the soil to produce soil-concrete. This produces a concrete column or post and similar columns or posts are formed side by side to produce a continuous wall.
The concept generally described avoids the necessity of having to excavate huge quantities of dirt in order to install a foundation or footing. It is particularly applicable to areas having sandy soil. Sand is a good material for producing concrete and it is difficult to excavate because the sides surrounding the cavity will cave into the cavity.
This concept has potential application for structures other than building foundations. One application is for producing trenches for laying pipe and is applicable especially where sandy soil conditions are encountered. Thus, parallel concrete walls are installed in the ground at each side of the proposed trench and the soil between the walls is thereafter removed. The concrete walls will prevent the soil from caving into the trench so that a pipe can be laid.
More recently there has been an increased appreciation for providing barriers in earth levees. Rivers offer many advantages to communities. They provide electricity, drinking water, irrigation water, attractive environment and recreation to name a few. However, every so often Mother Nature produces a combination of conditions that cause the rivers to overflow reeking havoc to these riverside communities. The damage caused by flooding can be somewhat controlled with levees. In those areas where a rising river would normally overflow its banks and cause significant damage, earth levees are provided along the river bank to confine the water flow to the banks. These levees can extend for a hundred miles or more. The requirement for massive volumes of material to create a levee renders it desirable to use the surrounding soil to construct the levees.
The surrounding soil is typically sandy and quite pervious to water. A soil-only levee will withstand short durations of flooding but experience has taught that prolonged flooding conditions will saturate the soil leading to erosion and destruction of the levee. The provision of an impervious barrier down the middle of the levee is desirable.
The concept of providing a concrete wall barrier along a levee using the above-described auger filling process is attractive but presents numerous problems. To name a few, the equipment used to install foundations is too heavy and not sufficiently mobile; concrete is not normally impervious to water without special treatment which adds undesired cost; preparation of the cement based grout on site provides problems. Solutions to these and numerous other problems that are encountered in adapting the auger filling process for producing elongated underground barrier walls is the primary objective of the present invention.